In sophisticated electronics systems such as those directed toward communications and industrial control, it is quite often the case that system integrators are confronted with disparate devices or resources which must be shared or multiplexed with one another. Interconnecting such equipment to facilitate efficient and straightforward operation may be a difficult task. In the industrial control environment, for example, networks are often employed to interconnect peer equipment under global control through a centralized computer system. Such a configuration may suffice in a simple system, but as the sophistication of the application increases, signal contention may arise especially if one piece of equipment must be shared by others. The conventional solution is to route all signals through a central computer which manages this contention. However, such a solution can introduce significant signal propagation delay, which tends to inhibit peer-to-peer communication among equipment controllers. This, in turn, lowers overall system efficiency.
Apart from high-level considerations such as the overall architecture used within an industrial control environment, low-level considerations also play a role in determining the success of a system integration involving equipment or resources from various manufacturers. For example, the voltage levels, polarities and current demands associated with a particular controlling device or apparatus may render it incompatible with other pieces of equipment. To maximize system efficiency, high-speed communication must occur directly between the various controllers and industrial resources rather than suffering propagation delays associated with routing through a centralized computer. An efficient architecture will impose a control mechanism upon these tools or resources without interfering with their communication links, once established.
Multiplexer-type circuits are available, but for several reasons are of limited utility for the specific problems herein addressed. Generally speaking, such devices only support 1-to-n or n-to-1 interconnections. As a consequence, simultaneous, asynchronous, bidirectional multi-wire connections among multiple resources are not easily realized. So-called analog multiplexer/demultiplexers, for example, while incorporating enable inputs to control communication between multiple, independent input/output (I/O) paths, rely on MOSFET-based transmission gates and, as such, do not perform requisite voltage/polarity matching. Moreover, it may be desirable to couple more than one I/O port to a common port simultaneously, a feature which is ordinarily undesirable with true multiplexing. Perhaps most importantly, independent bidirectional communication mandates the coupling of at least two lines per connection, facilitating simultaneous two-way transmission independent of the ground plane, a feature not offered with presently available digital or analog multiplexers.
Thus, there remains a need for a switching device which can facilitate and manage asynchronous peer-to-peer bidirectional communication. To take into account equipment or resources available from various manufacturers, such a switch would additionally perform signal level and polarity matching to ensure compatibility. An ideal switching unit would provide a modular building block to be connected in a variety of configurations so as to provide flexibility of network design, including daisy-chained, bussed, and hybrid architectural configurations.